Construction is the process of forming buildings and structures. Cranes, and particularly tower cranes, are commonly used in construction of buildings to move and transport materials in the construction site. Tower cranes are adapted to lift heavy loads to various heights. Buildings are generally constructed as a shell with portals, such as openings for panels or windows and the like. It is often required to lift, position, insert, off-load, collect and pull bulky objects and heavy loads through the portal, such as a vacant window opening, to various levels of a wall of a tall building under construction.
However, cumbersome, difficult to handle and elaborated maneuvers are often required for positioning the load within a confined or covered location, especially during windy conditions. A common technique to insert loads into a building, despite the substantial accompanied effort, time and expenses, an outward extension of the floor is built. Such an extension is built in order to off-load materials at a specific level or floor by vertically lowering a load onto the floor extension, disconnected from the crane hooks, and thereafter moved into the building for use. Other solutions involve extending the hoisting of a beam of an overhead crane. The hoisting beam, which extends from its fulcrum such that the load is placed at one end of the beam, for allowing maneuvering, positioning and insertion of the load through the portals into the different stories of the building. Such beams usually incorporate a balancing counter-weight, which requires its displacement along the beam to balance against the particular load which may differ from a hoisting task to another. Such solutions still require difficult and time consuming maneuvers, and consume the invaluable resources of the general hoisting apparatus, typically a tower crane, at the expense of its use for other hoisting tasks.
U.S. Pat. No. 8,840,158 to Leibovitz, entitled “Lifting Beam”, discloses an elongated load lifting beam with a balancing mechanism movably associated with the elongated beam and having a counterweight moved by movement apparatus for balancing the load.
French patent publication No. FR-2551738 to Theodor, entitled “Crane Spreader Bar for Hanging on the Hoisting Rope of a Crane, in particular a Building Crane”, discloses a crane spreader bar as an attachment for a building crane for enabling loads hanging on one end of a jib-like work-arm part to be placed into wall openings located high up on a building, in which crane spreader bar the horizontal equilibrium position between zero load and maximum load can be set by virtue of the fact that the linear division of the work-arm part and the power-arm part carrying the counterweight can be changed by motor-actuated displacement of the suspension device of the crane spreader bar relative to the crane spreader bar. The motor actuation to maintain the equilibrium position can be automated by a level-control system carried by the crane spreader bar and having a level switch.
U.S. Pat. No. 8,979,148 to Hatton II, entitled “Fly Jib for a Crane and Method of Use”, discloses a fly jib for a crane having a load block including a variable length beam to which a load can be connected. A rotation mechanism is connected to the variable length beam, and is connectable to the load block so that said rotational mechanism can selectively rotate the variable length beam with respect to the load block. A balance mechanism is connected to the variable length beam, the balance mechanism automatically keeps the variable length beam in a horizontal position.
U.S. Pat. No. 8,317,244 to Wesley, entitled “Apparatus and Method for Positioning an Object in a Building”, is directed to a hoisting and positioning apparatus comprising a rigid boom having a hook at a distal end thereof. The hoisting apparatus further includes a front mount having a front boom aperture and a rear mount having a rear boom aperture, each being adapted for confining the boom to slidably move. The apparatus has a slip collar having a slip collar boom aperture therein for receiving the boom there through and an offset hoisting apparatus attachment having a flexible linkage fixed at a distal end thereof with the slip collar. The boom is selectively slid between a retracted and an extended position and the load is secured to the hook. The crane apparatus then lifts and positions the load to a building.